Introduction to SEMIA, Version 3.0.1

SEMIA, version 3.0.1, is a tool for viewing time series of diagnostic and
morphology parameters of long-term ambulatory recordings, and ST
segment annotations with their corresponding ECG waveforms of the Long-Term ST Database (LTST DB). SEMIA was
created during the development of the LTST DB, a project supported by
Medtronic, Inc. (Minneapolis, MN, USA) and Zymed, Inc. (Camarillo, CA,
USA).

Compiling SEMIA

If you are running under GNU/Linux, you may not need to compile SEMIA.
Try running the precompiled version of SEMIA available here. (You will still need to have installed WFDB
and XView in order to do this successfully.)

If you need to compile SEMIA, make a directory for the SEMIA sources,
then copy all files from this directory into it. (For convenience,
you may download this gzip-compressed
tar archive of all files in this directory rather than downloading
the individual files.)

Enter your directory of SEMIA sources and type 'make'.

You may encounter many warnings related to improperly formatted
comments in XView #include files. These warnings may be ignored. If
you wish to eliminate them, download and apply this patch (read and follow
the instructions at the beginning of the patch to see how to apply
it).

When 'make' finishes, copy semia into a directory in your
PATH, and copy semia.opt and semia.hlp into
the directory where you wish to use SEMIA.

Using SEMIA

To run SEMIA successfully, the following files of the LTST DB are needed in the
current working directory:

snnnnn.hea (the header file for record snnnnn).
This file also contains comments of human annotators, diagnostic data of
the patient, and technical data of the record.

snnnnn.dat (digitized ECGs for the record)

snnnnn.cnt (numbers of annotated ST events and their
durations according to annotation protocols A, B, and C, and numbers of
normal and abnormal heart beats)

snnnnn_fin.dmy (time series of "fine" diagnostic
and morphology parameters obtained on average heart beats)

The last three of these files are contained within the .tsr.zip
files in the LTST DB directory on PhysioNet (or on the "Subset" CD-ROM).
Download the .tsr.zip file and unpack it using a command such as:

unzip s20011.tsr.zip

In addition, you will need copies of semia.opt (a text file containing
SEMIA's options) and semia.hlp (a text file containing on-line help
for SEMIA) in the current working directory, as noted above.

Run SEMIA by typing "semia". Click on the "Help" button to view
SEMIA's on-line manual. To open a record, click on "Open", then enter the
record name (snnnnn only; do not include .hea or any
other suffix in the record name). Depending on the speed of your system, it
may take up to a minute for SEMIA to load the data after you click "OK".

Once the data have been loaded, several buttons that were initially
inactive become available for use. Each of them ( "Lead0", "Lead1",
"Lead2", "Data", and "KL") opens a window when clicked. ("Lead2" remains
inactive unless you have opened a record with 3 ECG signals.)

Fine time series or functions are those obtained on average heart
beats after noise detection during preprocessing phase. Raw time
series or functions are those after resampling and smoothing of
fine functions.

Unsubtracted mode displaying ST level function (linearly interpolated
ST reference function is not subtracted from the ST level function).
In this mode, the active reference to compare ST segment waveforms is
a local reference annotation.

Subtracted mode displaying ST deviation function (linearly interpolated
ST reference function is subtracted from the ST level function to form
the ST deviation function). In this mode, the active reference to
compare ST segment waveforms is the global reference annotation

The ECG signal corresponding to current active reference annotation
is displayed in the upper part of the "Data" window.

Time series displayed in the "Lead" windows can be examined by
pointing them using mouse cursor or setting the Marker at the
time instance of interest. The corresponding ECG signal is displayed in
the lower part of the "Data" window.

ST segment annotations can be examined using the Exm option. The
examined ST annotation becomes the currently active annotation, and
its corresponding ECG signal is displayed in the lower part of the
"Data" window as well.

The time scale may be adjusted to permit between 1 minute and 96 hours
of data to be seen at once. Time series from "other" ECG leads may be
overlaid in each "Lead" window.

The "Data" window displays the ECG signal corresponding to the time
of the active reference annotation in the upper portion of the window,
and that corresponding to the time of the current active annotation or
marker in the lower portion of the window. These two ECG waveforms may be
overlaid. A variety of scales may be selected for comparing ST segment
morphologies. The time scale may be adjusted to permit between 1 and 60
seconds of data to be seen at once.

The center heart beat in each ECG trace is the beat average over the chosen
time window. ECG signals from "other" ECG leads may be overlaid.

The "KL" window displays time series of morphology (waveform shape)
parameters. Two sets of parameters (for the ST segment and the QRS complex)
can be displayed; the parameters are coefficients of a Karhunen-Loève
transform (principal components).

The ST segment or QRS complex distance function (Mahalanobis distance
function) can be overlaid in the KL window.